Exercise Benefits, Part 2: Why You Should Do Cardio
In all my years of teaching group fitness, I’ve found it pretty universally true that everyone falls into one—and only one—camp: you’re either a cardio person or a strength person. I can’t recall ever meeting someone who likes both equally.
On the one hand, as discussed in Part 1 of this six-part series, activity is activity, and anything is better than sitting around all day. So whether it’s running or lifting or doing an online workout, just move; it’ll be good for you. But on the other hand, each type of workout offers some unique benefits that you can’t get from the other—or at least that you can’t get to the same degree. This means that, regardless of which camp you fall in, to be the healthiest version of yourself, you need both cardio and strength.
This week, we’ll examine the benefits of doing cardio. For this article, when I refer to “cardio,” I’m talking about aerobic endurance exercise, such as jogging, cycling, dancing, walking, swimming, and the like—that is, activity that is mildly to moderately intense and that you’re sustaining for 30 minutes or more. Anaerobic cardio (i.e., short, high-intensity bursts) will be discussed in Part 4.
Benefits of (Aerobic) Cardio
All exercise can boost brain health and cognitive function (see Part 1), but cardio is, hands down (or up and down, if you’re doing jumping jacks), the type of exercise most consistently shown to lead to improvements in brain health. And this is because cardio doesn’t just boost cognitive function; cardio changes brain anatomy and physiology to help it function better.
Various forms of exercise have been shown to result in increased levels of a brain protein that helps grow and maintain neurons, but cardio most consistently yields these effects. Moreover, scientists have found that, at least in rat brains (because we can’t ethically study this in humans), cardio causes the greatest growth of new neurons in the brain, a process referred to as neurogenesis. Relative to rats that didn’t do any activity, rats that did strength had no increase in neurogenesis, rats that did intervals had a slight increase in neurogenesis, and rats that did cardio had three times as much neurogenesis. Brain imaging studies in humans have shown that aerobic exercise increases brain volume, suggesting that the same neurogenesis observed in rat brains is happening in our brains as well.
So not only does cardio improve cognitive function (e.g., memory, attention, executive control, processing speed, etc.), it changes the brain, suggesting that these improvements will last longer. This also means that cardio is one of the best ways to help prevent some of the inevitable cognitive decline we experience as we age. That is, cardio can make your golden years a little more golden.
Better Cardiorespiratory Fitness
In fitness, as in most of the rest of life, you get better at the things you do, and you generally have to do things to get better at them. Want to get better at the piano? Well, you’ll have to practice the piano. Want to become fluent in a second language? You’ll need to study that language. Want to improve your cardiovascular health? You’ll need to do cardio.
Aerobic cardio, such as a virtual dance class, works our hearts and lungs in an endurance capacity more than any other type of exercise. When you’re jogging or swimming at a consistent, mild to moderately high level of intensity (Zones 1 through 3, if you want to think of it in terms of heart rate zones; see the chart below for a quick reference guide on the zones), you’re putting a constant demand on your cardiovascular and respiratory systems. In response to this demand, your body adapts, resulting in improvements in your cardiorespiratory fitness.
This increased cardiorespiratory fitness could include any (and probably all) of the following benefits: lower blood pressure, lower resting heart rate, increased heart muscle mass, higher stroke volume (i.e., amount of blood pumped with each contraction), and increased VO2 max (i.e., lung capacity). Aside from being signs of good health and fitness, these changes also mean that your body can transport the needed energy and oxygen to the muscles that need them, meaning those muscles will have the metabolic resources to have more endurance.
Having cardiorespiratory stamina is only one piece of endurance. We also need our muscles themselves to have stamina. While strength and interval training can be great ways to cross-train your muscles for endurance, ultimately, if you want to improve your endurance, you need to train endurance; you need to do cardio.
This is because our muscles are made up of different types of fibers. Slow-twitch fibers are the ones we use when we do cardio because they work aerobically and have more stamina. Fast-twitch fibers are the ones that we use for strength because they generate more force; however, they don’t last as long (hence the muscle fatigue you feel when you do strength training). Some of these fast-twitch fibers work aerobically, while others work anaerobically. (Perhaps more on that in another article someday.)
The point is this: just like you can’t strengthen your leg muscles by only doing biceps curls, you won’t strengthen your slow-twitch fibers by only doing strength. To train the slow-twitch muscles, you need to work those muscles. Thus, you need to do cardio to build endurance from both a cardiorespiratory and a muscular perspective.
More Fat Burning (in the Moment)
I’ll save a more in-depth discussion of heart rate zones and metabolism for another article (or few; we’ll see), but I’ll touch on this a bit to highlight one key benefit of cardio: if it’s a low or moderate level of intensity (i.e., Zone 1 or 2), cardio is the best type of exercise for burning fat while exercising. This is because, at the lower-intensity zones, your body can predominantly use fat as fuel.
However, because fat is slower to metabolize than sugar, as you go into the higher zones, where your body needs more energy more quickly, you burn more sugar. Therefore, if you want to maximize your fat-burning, keep the intensity mild to moderate, like a brisk walk or an easy online cardio workout.
Cardio can be the best at improving your coordination, largely due to the activities we do to get cardio. Activities such as dance (check out our online dance instructors) and kickboxing comprise full-body, coordinated movements; doing these (and similar) activities will help improve your coordination at a neuromuscular level as your brain and muscles work together to produce the movements.
The bonus of doing such choraographed cardio workouts is that it also benefits our brains because they similarly get worked out by the challenge of following the choreography.
Any exercise can help promote sound sleep, but cardio is the winner. While scientists don’t know the exact mechanisms, cardio increases the amount of sleep you get in the deeper sleep stages, the ones where your body and brain get a chance to recover and rejuvenate. Our bodies need sleep, so getting this sound, deep sleep will lead to a whole host of other benefits: clearer mind, more energy, less inflammation, and more.
But be careful: if you exercise right before bed, you might disturb your sleep. Cardio raises our endorphin levels (endorphins make us feel energized) and our core body temperature. We sleep better when our core body temperature is a little lower, and when our minds are calmer, so try to finish your workout at least an hour before bedtime.
It’s challenging to make claims about exercise type and mood, because most of the research looking at the effects of exercise on mood has only looked at cardio. However, based on the research that has compared the different forms of exercise, it seems to be that cardio is more effective at improving mood.
My own experience confirms this: I’ve had my share of runners highs, but I’ve never gotten that same feeling from HIIT (and I love HIIT). But it’s not just me. The fact that there is such a thing as a runner’s high and no such thing as a lifter’s high suggests that sustained, lower-intensity exertion is the sweet spot for those good feelings.
That being said, there is evidence that exercise’s mood benefits might be tied to the exerciser’s enjoyment of the exercise. So if you enjoy doing strength training, then lifting might boost your mood more than running would. Other evidence shows that, at least for older adults, strength training is associated with the greatest improvements in mood, but this may be a side-effect of how resistance training, more than cardio, can improve quality of life for the elderly (i.e., strength training improves their strength and bone density such that they’re less likely to fall, and, if they do, they’re less likely to get seriously injured and are more likely to be able to get back up).
Cardio is arguably the best form of exercise for your mental health (mood, cognitive function, and brain health), and it just might be the best for reducing your risk of various diseases, because it improves pretty much all the risk factors (stress, inflammation, blood pressure, body fat, etc.).
At the very least, it’s one of the only types of exercise you can safely do at a high frequency—even every day, if you wanted—without running significant risks of overtraining or injury. For these reasons, cardio deserves a good chunk of your designated activity time each week, whether that's running or doing an online dance class or kickboing workout at home.
So if you’re adamant about only ever doing one type of exercise (which I advise against with equal adamance, as do several of the articles linked below), make it cardio. But if you want to maintain a healthy, active lifestyle into your golden years, you’ll need strength, too. Read the next article in the series, Exercise Benefits, Part 3: Why You Should Do Strength Training, to see why.
And if you’re thinking about how you can do your cardio workouts at home to get these benefits, check out ZentasticFit.com! Our platform has many online instructors. From dance to strength to yoga to barre, there are so many options, and they have a vast array of experience to help you reach your fitness goals and provide you with individualized, custom workout routines and programs tailored to your body, your goals, and your lifestyle.
“Cardio vs Weights”, Kristen Barta (reviewed by Peggy Fletcher) (Healthline)
“Customizing a Cardio Plan to Work in Your Favor”, Paul Kriegler (Life Time)
“Exercising for Better Sleep” (Johns Hopkins Medicine)
“HIIT vs Continuous Endurance Training: Battle of the Aerobic Titans”, Micah Zuhl and Len Kravitz (University of New Mexico)
“4 Differences in How Cardio and Strength Affect Your Health”, Ruben Castaneda and K. AleishaFetters (U. S. News)
Or, for an educational video, check out Wendy Suzuki’s TED talk on how exercise changes our brains
By Dustin R. Meriwether